Setting the scene. Help your new cat settle into your home by keeping them in a small room with a litter box, food, water, toys, and a safe place to hide (such as a cat carrier with a towel inside). Choose a room that doesn’t interrupt your resident cat’s routine. Let them become comfortable there for three or four days.
Do not allow the cats to interact during this time. However, it is fine for the cats to be sniffing under the door and investigating. Switch bedding and other items that have the scent of each of the cats on them. This way each cat can become used to the scent of the other without meeting face to face.
Spend quality time with each cat on either side of the door—petting, playing, and relaxing. Again, this will allow them to be aware of each other in a non-stressful situation. This is often reassuring to both cats.
Signs of stress. If at any point the hissing is intense, or either cat is growling, continue to keep them separate for as long as it takes the upset cat(s) to settle down. Other signs of stress are: not eating, not using the litter box appropriately, over grooming, etc. If these symptoms are apparent in your resident cat, please call your veterinarian. If the adopted cat shows these signs, please contact the SF SPCA. This may mean that the separation needs to last a week or more. If the cat’s interaction is more intense than you feel is normal, please contact the SF SPCA.
If there is no intense hissing from either cat (i.e. loud hissing with wide-open mouth and teeth showing, or multiple hisses), prop the door open about an inch to allow the cats to view each other without being able to make contact. Leave the door like this for a few days. Watch their interactions; if no serious hissing or aggression is noted, then it’s time for the next step.
First interactions. If the sniff visits are going well, it’s time to start supervised interactions. Open the door and let the new cat come out and explore. Let the cat come out of the room at their own pace. Forcing the cat to come into a new territory will just make the cat increasingly tense and prolong their insecurity. Let the cats enter each other’s territory for about a half hour. Then separate the cats and repeat this process a few times each day.
If a cat seems overly stressed about the other cat, you can distract the cat with toys or food treats, but be sure to keep the toys four or more feet apart when playing. Sometimes cats play so hard that they forget to be upset about the other cat and start to become accustomed to the other cat’s presence. There may be rivalry for toys, so this may not always work. Treats may also help alleviate this situation, so be sure to give them treats in the presence of the other cats. This will not only distract them, but it will also serve as a reward for not hissing.
At the end of the play or treat session immediately separate the cats. This time apart allows them to be able to process the information they gained while they were together. It also allows them both to regain their sense of territory and confidence, which encourages a favorable interaction at their next meeting. Continue this process daily, lengthening the amount of time they are together a little each session.
Never punish a cat for aggressive behavior toward another cat. Most owners do this thinking they will teach the cat that the aggressive behavior is inappropriate, but it only ends up making the cat more stressed and upset, prolonging the cat-to-cat aggression. The best way to react is either to stay silent, and calmly separate the cats, or to speak softly to the cats.
Extra Steps for a Shy Kitty
If the new cat is shy, the introduction must be taken more slowly. The cat will need extra time to settle into their new environment, and to feel comfortable in their safe room. It may be necessary to repeat the introduction and separation program several times. This separation time is also an excellent time for you to bond with each cat, one at a time, so that they do not over-bond to each other.
When ready, open the door and allow the cats to interact on their own time. Do not force either cat to go from one space to another.
Supervise their interactions. Only let them interact for short sessions: ten to fifteen minutes at a time. Then separate them again. Do this several times a day until you are sure they are tolerating the presence of the other cat, and not fighting, chasing, or watching the other cat intensely. Do not leave them alone together until you are reasonably certain that they will not hurt one another.
Introductions often take time. Some cat-to-cat introductions go very smoothly, while others may take weeks or months before the cats learn to tolerate each other. The best thing to do is to go as slowly as necessary—don’t rush the introduction. Please remember that you are hoping and working for a very long-term relationship; being patient at first will pay off! Rushing the introduction will often cause serious problems which may take longer to solve—or in some cases, may never be solved.
Finally, most cats will adjust to living within a multi-cat household. Like people, some will enjoy it more than others. Patience on the part of all concerned will be more likely to produce an enduring peace than anything else. Enjoy your kitties!